Microstructural, porosity and mechanical properties of lap joint laser welding for 5182 and 6061 dissimilar aluminum alloys under different place configurations

This paper studied the dissimilar aluminum alloys (5082/6061) laser lap welding with different configurations. Two configurations were set up by exchanging the place position of the upper and lower plates under the same parameters. When higher Mg content alloy located as the upper plate, the evaporation of Mg led to the instable welding process and the lower actual heat input, which affected the weld morphology. The solidification microstructures near the fusion line of the two joints were observed by SEM and analyzed by coupling temperature field and phase field method simulation results, longer and wider intergranular liquid channels and more severe solute segregation occurred in 6061/5182 joint. The results validated that 6061/5182 joint had a higher crack sensitivity than 5182/6061 joint. Moreover, crack sensitivity had a greater influence on tensile property than other factors by testing. The two joints presented significantly different porosity and pore morphology. Dense and fine pores appeared when more Mg element content in the upper plate, which related to the failed escape of Mg vapor and the attenuation of laser energy in thickness direction. Moreover, microhardness decreased as Mg element content increasing, because of the dilution effect of the strengthening phases. (C) 2020 The Authors. Published by Elsevier Ltd.